Water Level Indicator Circuit using Transistors

The water level indicator circuit using transistors is a simple circuit that is used to detect and indicate the level of water in the overhead tank. All the householders are storing the water in overhead tanks for later use. When we store the water in the tank, no one can identify the level of water. So, due to overflow in the water tank, there is a wastage of energy and water. A water level indicator is used to resolve this problem. The water level indicator circuit can be made at home very easily and it can also be purchased from the market very easily. The water level circuits are used in the homes, factories, chemical plants, and electrical substations and also in other liquid storage systems.
Water Level Inidcator using Transistor

Define Water Level Indicator?

The water level indicator using transistors is a system that gets information about the water level in tanks which is used in homes. By using the water level indicator we can overcome the overflow problem of water from the tankers.

Water Level Indicator Using BC 547 Transistor

Water level indicator circuit using transistors can be designed easily by using any kind of transistors. in this device we are going to using NPN transistors BC547. Before starting to design the circuit, gather the following components according to the given below detail.

Components Detail

  • Transistor – BC 547 (4 transistors)
  • Resistors- 4, 220 Ohm
  • LEDs- 3
  • Buzzer-1
  • Battery- 5-9 V or adoptor

Circuit Explanation

BC 547 is an NPN bipolar junction transistor that is used to amplify current. In this device, we have used BC 547 transistors as a Switch. We have created 4 different levels of water level detection namely A, B, C and D. We have connected 3 LEDs and a buzzer. Whenever the level of water reaches point A, transistor Q1 is turned ON and Red LED starts glowing. When the level of water reaches to B point Transistor Q2 is turned ON and the yellow LED starts glowing. As the water level reaches point C, the transistor Q3 is turned ON and the green LED starts glowing. similarly, when the water level reaches point D, Transistor Q4 is turned On which triggers the buzzer starts beeping indicating that the tank is full. We can create different levels of water detection using more transistors and LEDs.


In this circuit, the BC547 is used. We have attached resistors of 100 Ohm at the base of transistors Q1, Q2 Q3 to protect the transistor from burning from high current across the LEDs. When there is no current on the base of transistors current does not flows from emitter to collector that is way LED will remain OFF.
When the water level reaches the point A, a very small current (conductive current) is created between the base of transistor Q1 and the positive terminal of the battery. Therefore, the Collector and Emitter of Q1 connected. As soon as the positive voltage is applied at the base of transistor Q1, the transistor Q1 is turned on and the RED LED starts glowing. Similar all transistors turned on as conductive current from the base is applied with water. All transistors turned on when the tank is full. The buzzer will be turned on as Q4 turned on which indicates that the tank is full.

Features of Water Level Indicator Circuit using transistors:

  • Consumes very little current/power
  • Low maintenance
  • Easy installation
  • Portable and compact design
  • Fully automated
  • Fully modify able


Water storing is one of the most important tasks. Due to the overflow of water tanks, a large amount of water is wasted almost everywhere. The water level indicator project is one of the best solutions to protect the water from wastage. From the following given points, you can easily understand the importance of water level indicator
  • By using this circuit and doing little modification we can control our water pump automatically.
  • This is a very simple water level indicator and it can also be used for a liquid level indicator in huge containers.
  • It can also be used in fuel level indicator in motor vehicles. (But you should not use this circuit in fule measurement use a built-in circuit for fule.

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